Novel Non-invasive Evaluation of Oxygen Deficit Before and After Thoracentesis - A Pilot Study

Pyarali FF and Cohen SE

Published on: 2023-10-11

Abstract

Rationale

Pleural effusions commonly lead to dyspnea, and symptom improvement after thoracentesis has been noted. Some studies show that the removal of fluid improves ventilation-perfusion matching, while others have noted symptom improvement by improving respiratory mechanics. A novel method to non-invasively measure the arterial oxygen content has emerged, with studies showing a strong correlation with invasive arterial oxygen measurement. We utilized this technology to evaluate differences in oxygen deficits before and after thoracentesis.

Methods

Patients undergoing routine therapeutic thoracentesis due to various etiologies were recruited. Oxygen saturation, end-tidal CO2, and calculated oxygen deficit were measured before and after thoracentesis.

Results

A total of 19 patients were recruited, from which 20 measurements were taken. The median age was 67.1 years (59.7–78.1 IQR), and 35.0% of patients were female. The median oxygen saturation prior to the procedure was 97.0%, and the median oxygen deficit was 10.5%. After thoracentesis, median oxygen saturation only improved by 1.0%, calculated PaO2 improved by 2.50 (p = 0.77), and median oxygen deficit improved by 2.5 (p = 0.58). Patients with malignancy were more likely to have a worsened oxygen deficit after thoracentesis, but this was not statistically significant (OR 0.50, p = 0.47). The total pleural fluid removed was not significantly associated with changes in oxygen deficit (p = 0.75).

Conclusion

Calculating the oxygen deficit before and after thoracentesis demonstrated trends towards improvements that were not statistically significant. The lack of significant improvement in oxygen deficit may suggest that dyspnea in recurrent pleural effusions is more a function of impaired respiratory mechanics than gas exchange impairment.